BSI Standards Publication National Annex to Eurocode 1 Actions on structures – Part 1 7 Accidental actions NA+A1 2014 to BS EN 1991 1 7 2006+A1 2014 Incorporating corrigendum August 2014 NA+A1 2014 to[.]
Trang 1BSI Standards Publication
National Annex to Eurocode 1: Actions on structures –
Part 1-7: Accidental actions
Trang 2Publishing and copyright information
The BSI copyright notice displayed in this document indicates when the document was last issued
© The British Standards Institution 2014
Published by BSI Standards Limited 2014 ISBN 978 0 580 87765 0
ICS 91.010.30, 91.080.10, 93.040 The following BSI references relate to the work on this standard:
Committee reference B/525/1 Draft for comment 07/30128330 DC
Publication history
First published December 2008
Amendments/corrigenda issued since publication
31 July 2014 National Annex revised due to CEN Amendment A1:2014
31 August 2014 Erroneous text in NA.2.34 removed
Trang 3Contents
Introduction 1
NA.1 Scope 1 NA.2 Nationally Determined Parameters 1 NA.3 Decision on the status of informative annexes 13
NA.4 References to non-contradictory complementary
information 14
List of tables
Table NA.1 – Equivalent static design forces due to vehicular impact
on members supporting bridges or CC3 buildings over or adjacent
to roads 3 Table NA.2 – Influence of class of road below bridge 4 Table NA.3 – Minimum traffic flows to be used to determine F2 5 Table NA.4 – Influence of speed limit under bridge 5
Table NA.5 – Influence of junctions 6 Table NA.6 – Influence of clearance 6 Table NA.7 – Number of columns for each support type 7 Table NA.8 – Deck stability 7
Table NA.9 – Equivalent static design forces Fdx due to impact on
superstructures 9 Table NA.10 – Equivalent static design forces Fdy due to impact on
superstructures 9
Trang 5National Annex (informative) to
BS EN 1991-1-7:2006+A1:2014, Eurocode 1: Actions on structures – Part 1-7: Accidental actions
Introduction
This National Annex has been prepared by BSI Subcommittee B/525/1, Actions (loadings) and basis of design and it is designed in the UK
to be used in conjunction with BS EN 1991-1-7:2006+A1:2014 The start and finish of text introduced or altered by national amendment A1:2014 is indicated in the text by
NOTE This National Annex refers to design values for accidental actions
In the UK National Annexes to BS EN 1990:2002+A1:2005 Annex A1 and Annex A2, the safety factors for accidental actions are equal to 1 Therefore the nominal value and the design value for accidental actions are numerically the same The nominal values and design values of an
action are defined in BS EN 1990:2002+A1:2005 1.5.2.2 and 1.5.3.21
respectively.
NA.1 Scope
This National Annex gives:
a) the UK decisions for the Nationally Determined Parameters described in the following subclauses of
BS EN 1991-1-7:2006+A1:2014:
— 3.3 (2) — 4.5.1.2 (1) — 4.6.2 (3)
— 3.4 (1) — 4.5.1.4 (1) — 4.6.2 (4)
— 3.4 (2) — 4.5.1.4 (2) — 4.6.3 (1)
— 4.1 (1) — 4.5.1.4 (3) — 4.6.3 (3)
— 4.3.1 (1) — 4.5.1.4 (4) — 4.6.3 (4)
— 4.3.1 (2) — 4.5.1.4 (5) — 4.6.3 (5)
— 4.3.1 (3) — 4.5.1.5 (1) — 5.3 (1)P
— 4.3.2 (1) — 4.5.2 (1) — A.4 (1)
— 4.3.2 (2) — 4.5.2 (4)
b) the UK decisions on the status of
BS EN 1991-1-7:2006+A1:2014 informative annexes; and c) references to non-contradictory complementary information
NA.2 Nationally Determined Parameters
[BS EN 1991-1-7:2006+A1:2014, 2 (2)]
All accidental actions are free actions unless otherwise stated in the individual project
Trang 6NA.2.2 Notional values for identified accidental actions
[BS EN 1991-1-7:2006+A1:2014, 3.1 (2) Note 4]
Values for accidental actions should be as given in
BS EN 1991-1-7:2006+A1:2014 and this National Annex
[BS EN 1991-1-7:2006+A1:2014, 3.2 (1) Note 3]
The level of acceptable risk should be determined on a project specific basis Recommendations for acceptable risk levels for road, footway and cycletrack bridges, are contained in PD 6688-1-7
[BS EN 1991-1-7:2006+A1:2014, 3.3 (2) Note 1]
For building structures the recommended model should be used
[BS EN 1991-1-7:2006+A1:2014, 3.3 (2) Note 2] For building structures, the indicative limits should be used See A.4 of
BS EN 1991-1-7:2006+A1:2014
Text deleted
failure [BS EN 1991-1-7:2006+A1:2014, 3.3 (2) Note 3] For the design of building structures the three approaches given in 3.3
(2) of BS EN 1991-1-7:2006+A1:2014 may be used as appropriate and
as specified in Annex A of BS EN 1991-1-7:2006+A1:2014
[BS EN 1991-1-7:2006+A1:2014, 3.4 (1) Note 4]
For the design of building structures the categorization given in Table A.1 of Annex A of BS EN 1991-1-7:2006+A1:2014 should be used
[BS EN 1991-1-7:2006+A1:2014, 3.4 (2) Note]
For the design of structures for higher and lower consequence classes, the requirements should be determined for the individual project
[BS EN 1991-1-7:2006+A1:2014, 4.1 (1) Note 1]
Recommendations for accidental actions on lightweight road structures are given in PD 6688-1-7
[BS EN 1991-1-7:2006+A1:2014, 4.1 (1) Note 3]
Recommendations for transmission of impact forces to foundations are given in PD 6688-1-7
Trang 7NA.2.11 Values of vehicle impact forces
[BS EN 1991-1-7:2006+A1:2014, 4.3.1 (1) Note 1]
For buildings adjacent to roads, and in the absence of mitigating measures, the indicative equivalent static design force due to vehicular impact given in Table 4.1 of BS EN 1991-1-7:2006+A1:2014 may be used, unless the structure is in Consequence Class 3 (CC3) For CC3 buildings the equivalent static design force should be taken
from Table NA.1 and applied in accordance with NA.2.11.2.2.1 Other sub-clauses from NA.2.11.2 are applicable to road structures and for CC3
building structures where approval is obtained on an individual project basis. The adjustment factor for buildings should be taken as 1.0
For buildings in CC1 and CC2 see also NA.2.13.
For members supporting structures over or adjacent to roads the equivalent static design forces due to vehicular impact should be in
accordance with NA.2.11.2.2 to NA.2.11.2.4 Alternatively, where safety
barriers are provided, recommendations are given in PD 6688-1-7
Table NA.1 Equivalent static design forces due to vehicular impact on members supporting bridges or
CC3 buildings over or adjacent to roads
Force Fdx
in the direction
of normal travel
Force Fdy
perpendicular to the direction of normal travel
Point of application on bridge support
Bridges over Motorways, Trunk and Principal Roads
Main component 1650 825 At the most severe point between 0.75 m
and 1.5 m above carriageway level Residual component 825 415 At the most severe point between 1 m
and 3 m above carriageway level
Bridges over other roads where speed limit ≥ 45 mph (72 kph): e.g Other Rural Roads
Main component 1240 620 At the most severe point between 0.75 m
and 1.5 m above carriageway level Residual component 620 290 At the most severe point between 1 m
and 3 m above carriageway level
Bridges over other roads where speed limit < 45 mph (72 kph): e.g Other Urban Roads
Main component 825 415 At the most severe point between 0.75 m
and 1.5 m above carriageway level Residual component 415 205 At the most severe point between 1 m
and 3 m above carriageway level
Bridges over roads: minimum forces for robustness
Main component 250 250 At the most severe point between 0.75 m
and 1.5 m above carriageway level Residual component 165 165 At the most severe point between 1 m
and 3 m above carriageway level
Trang 8NA.2.11.2.2 Accidental actions caused by road vehicles – Impact on
supporting substructures for road bridges
NA.2.11.2.2.1 The equivalent static nominal collision forces are given
in Table NA.1, together with their direction and height of application, and should be considered to act horizontally on bridge supports The main and residual load components should be applied simultaneously
Refer to NA.2.14 for the application rules for Fdx and Fdy The controlling class of road is the road under the bridge, i.e the road that is carrying the Heavy Goods Vehicles (HGV) that might impact on the support
NA.2.11.2.2.2 The equivalent static design forces given in Table NA.1
should be multiplied by an adjustment factor Fa in accordance with
NA.2.11.2.4, which is based on the risk assessment procedure given in NA.2.11.2.3
NA.2.11.2.2.3 In all cases, the larger of the adjusted values for
the main and residual components, and the minimum forces for robustness specified in Table NA.1 should be used.
NA.2.11.2.3.1 A risk ranking factor Rde should be calculated for each bridge support location
NA.2.11.2.3.2 Where supports are exposed to impact from more than
one traffic stream containing HGVs, values of Rde should be calculated independently for each traffic stream and the total Risk Ranking
Factor Rde should be obtained by taking the sum of these independent
Rde values
NOTE 1 A “traffic stream” includes all traffic flowing in any one direction on any one carriageway Thus a support adjacent to a single carriageway road with bi-directional flow would have a separate contribution to R de from two traffic streams A support on one side of a dual carriageway road would have contributions to R de from one traffic stream, whilst a support in the central reserve would have contributions
to R de from two traffic streams.
NOTE 2 Where additional protection in lieu of strengthening is to be provided, the risk from each side should be considered separately and protection provided on each side appropriate to the risk on that side only.
NA.2.11.2.3.3 The risk ranking factor R de is given by:
Rde=F F F F F F F F1 2 3 4 5 6 7 8
The requirements for determination of F1 to F8 factors are given in
NA.2.11.2.3.4 to NA.2.11.2.3.11
NA.2.11.2.3.4 Road class below bridge F1
The risk of a traffic accident, which might lead to an HGV impact on a bridge support, depends on the class of road below the bridge
Table NA.2 Influence of class of road below bridge
i) Motorways and dual carriageway Trunk Roads ii) Single carriageway Trunk Roads
iii) Principal Roads (In Northern Ireland non trunk
A roads) iv) All others
0.66 1.25 1.25 2.63
Trang 9NA.2.11.2.3.5 Factor for HGV flow under bridge F2
F2 = (AADTunder × percentage of HGVs)/(25 000 × 7,8%) The annual average daily traffic under the bridge (AADTunder) includes all traffic in the traffic stream beneath the bridge for which this contribution to the risk ranking factor is being assessed (see
NA.2.11.2.3.2) The traffic flow is expressed as 24 h annual average
daily traffic (AADT), i.e total annual traffic divided by 365
The value of AADTunder should be the higher of the measured flow and
of the assumed flow for the class of road, given in Table NA.3 Where
no existing flow information is available, the flows from Table NA.3 should be used The AADT values presented in Table NA.3 are the flows in one direction (for example one traffic stream on a two-way road) as appropriate for the support under consideration
The proportion of HGVs in the traffic should be obtained from existing data where available For example, the Department for Transport (DfT) publishes maps to show AADT and percentage of HGVs for motorways and trunk roads in England Alternatively, the proportion may be deduced from data for similar roads nearby Where
no information on the proportion of HGVs is available (for example from a traffic survey), 7,8% should be used
NOTE HGV count is taken as equal to the number of all vehicles that have three or more axles It may be assumed that 40% of the UK HGV population comprises two-axle rigid vehicles Where the number of HGV
is obtained from published transport statistics, this number has to be multiplied by 0.6 before being used in this National Annex.
Table NA.3 Minimum traffic flows to be used to determine F2
one traffic stream
F2 assuming 7,8% of HGV
ii) Wide Single Carriageway 2 lane 7 000 0,28
NA.2.11.2.3.6 Factor for speed limit under bridge F3
Table NA.4 Influence of speed limit under bridge
iii) 50 mph (80 kph) or less 0,75
This allows for differences in the severity of impact due to the variation in speed limit for particular road types (for example urban motorways) The next lower class of speed limit may be considered in locations where speed is effectively restricted by specific features such
as, for example, roundabouts or traffic lights
Trang 10NA.2.11.2.3.7 Factor for distance (D) of bridge support from nearest junction on the road under the bridge F4
Table NA.5 Influence of junctions
iii) 100 m ≤ D < 200 m (including structures at
interchanges)
0,2
iv) D ≥ 200 m (including sections of carriageway remote from junctions)
0,95
Distance D is measured in a direction parallel to the line of the road
under the bridge from the nearest point at which lane markings for the converging or diverging roads meet
NA.2.11.2.3.8 Factor for clearance (C) F5
Table NA.6 Influence of clearance
Clearance C is measured from the centre of the nearest running lane
ordinarily used by HGVs to the front face of the support Hence, on a motorway, the hard shoulder is included in the clearance for supports adjacent to the left hand lane and, for supports in the central
reservation, the right hand lane is included in the clearance if HGV travel is legally prohibited from that lane
Note that if a carriageway is only used in maintenance situations or any part of the carriageway (for example the hard shoulder) is only opened to normal traffic for a specific period, such as at times of peak traffic flow, it should not be considered as a running lane for the
purposes of calculating F5
The value of C should be determined by multiplying the horizontal
distance in metres by 0,6 if the ground level at the face of the support
is lower than the centre of the nearest running lane by more than 10% of the clearance, and by 1,6 if the ground level at the face of the support is higher than the centre of the nearest running lane by more than 10% of the clearance
Additionally, the value of C should also be determined by multiplying
the horizontal distance by 0,6 if the support is alongside a road that has a gradient greater than 4% downhill and by 1,6 if the support is alongside a road that has a gradient greater than 4% uphill
Trang 11NA.2.11.2.3.9 Factor for number of columns F6
Table NA.7 Number of columns for each support type
Risk of collapse of the bridge following partial failure of a support is significantly reduced if the number of columns provided is more than one (note that the use of longitudinally divided decks can increase the
value of F6)
Leaf piers (supports that have a length along the carriageway similar
to the width of the main structure above ignoring edge cantilevers)
are to be treated as single columns The relatively high value of F6 for leaf piers will usually be counteracted by their relatively high impact resistance
NA.2.11.2.3.10 Factor for stability of deck F7
Table NA.8 Deck stability
i) Continuous spans:
a) With sufficient strength over the piers
to prevent bridge collapse after impact:
verified by quantitative assessment b) With sufficient strength over the piers
to prevent bridge collapse after impact:
assessment by engineering judgement c) Without sufficient strength over the piers to prevent bridge collapse after impact
1,0
1,5
2,0
iv) Simply supported spans, including spans supported on cantilevers
2,0
NA.2.11.2.3.11 Consequence factor for road bridges F8
F8 = (1 200 + AADTunder × 0,006 + AADTover × 0,2)/6 300 Values of AADT should be calculated in a similar manner to that used
in deriving F2 However, in this case AADTover includes all traffic in the stream or streams that use the part of the bridge deck structure that might collapse following failure of the support, and AADTunder also includes all traffic in the traffic stream or streams whose passage will
be obstructed following the collapse
NOTE Where the bridge over can be split into separate decks for each carriageway, the AADT over over will be for one traffic stream
In cases where many pedestrians are expected to use the footway(s)
at frequent intervals, for example for access to major public assembly facilities such as schools, sport stadiums, and public transportation
facilities, the value of F8 should be increased by adding a value of 5